I'm with Mick F. I also used to commute with an old halogen plastic "miner's lamp" on the front fork. There were many bad things about those lights compared to modern LED dynamo ones, such as difficulty of keeping them watertight and keeping the batteries in place as I skittered along country lanes, but shadows thrown by the wheel was never one. I'm unsure what Brucey's lamp, fork and/or wheel did to cause that, but don't let one bad implementation set you against the concept - even if I prefer the crown (protected by a mudguard), the leg is still far better than a light mounted too high, not straight and not level on a crowded handlebar. Handlebars are for hands.
Brucey wrote: mjr wrote:
Brucey wrote:FWIW most motorcyclists live in fear of being SMIDSY'd and they are lit up like a christmas tree.
And being lit up like a tree doesn't seem to be working for them, so I'm not sure that's a great argument!
my point is that most motorists are looking out for cars
not two wheelers of any kind, and making yourself less visible by having a lamp that can be obscured from some angles isn't going to help matters one bit.
And my rebuttal is that few lamps are as easily obscured as you are suggesting.
Brucey wrote: Riding around with only a fork-mounted lamp that is definitely obscured from certain angles is not going to improve your life expectancy.
It'll certainly improve it more than riding around without any lights! Of course, don't mount it high enough that the top of the rim will block the lamp over a wide area of other road user head heights, but the obscuring of a lamp mounted low on the fork will be minimal and fairly far ahead of the bike. Oh and I just remembered: for the above to apply, it's important that the illuminated surface area (lens or reflector, depending on design) is wider than the tyre!
not quite as simple as that; the reflector/lens is usually designed to throw a beam of some kind and there is no guarantee that light thrown from the periphery of the lens/reflector is going to be thrown anywhere other than forwards. In many cases the light that emerges at an angle to the main beam (and renders you visible at an angle from side turnings) only
comes from a small proportion of the light. You can gauge if this is the case by looking at the shadow that is cast by the front wheel; a well defined shadow essentially means a small effective emitter. Anyone within the shadow area won't be able to see the light. If the light emits strongly at an angle over the full diameter of a large lens then there would be no real shadow. IME this never happens, and worse yet deep aero section rims and fatter tyres mean the rim/tyre is more than ever capable of obscuring a fork mounted light.
The light reaching motorists' eyes should never be from the main beam on a standard light... well, not unless the motorist is in a very low sports car with their eyes below the cutoff height. The light they see is always from the so-called spill (that which illuminates reflective road signs) that basically appears as the glowing lens/reflector face, which is why I say it's important for that face to be wider than the tyre. That width is essentially why the front wheel throws no full shadow, only penumbra.
If you use a fork boss for a lamp there is usually a shadow cast at an angle of twenty or thirty degrees to one side.
Thirty degrees? That seems to mean that your fork lamp boss is wide or high or projects a long way forwards:
Distance of 622mm tyre bead in front of a low lamp mounting point on a typically-raked fork = 300mm
Width of front hub between dropouts = 100mm
Width of example front tyre = 32mm
So the left edge of the light is (100+32)/2 mm = 66mm to the right of a plane touching the left edge of the tyre.
Projecting a line back thirty degrees from there until it is 300mm back puts it (300 / √3)mm = 173mm right of that plane = 107mm right of the dropout.
I don't remember seeing many fork mounts that put the left edge of the lamp that far out - most are pretty close to the leg.
Of course, if you put the light higher up or used deeper rims, it wouldn't need to be mounted so far out before the wider sloped section of the tyre/wheel could block a wider lamp face, which is why I say mounting low (the centre third of the wheel height, say) is important.
My suggestion is that if you use a lamp like this, add a flashing LED or something higher up, that can be seen; it might save your life. If you use a fork mounted lamp only, from choice, then IMHO you are taking a pointless risk.
"it might save your life"? I've been a big fan of some of Brucey's technical posts, but I am really disappointed to read such scaremongering being used to try to support geometry that just doesn't stack up.
My suggestion is to prefer a fork crown mount, but if you need to use a traditional leg mount for some reason, then prefer a wide-faced lamp mounted low. Don't bother with pointless blinkies - they're just another light to look after for little benefit because anyone who doesn't see a lamp you can see with probably isn't looking anyway, so won't see a handlebar blinky either. Spend the time and money addressing real risks instead.